The present invention relates to a method for controlling a hydraulic drive system, in particular of a crane or a construction machine, which comprises a closed hydraulic circuit with a hydraulic pump and a hydraulic motor, in which in dependence on a desired value of an output parameter of the hydraulic circuit an actuating signal is provided for adjusting the hydraulic pump and/or the hydraulic motor. The invention furthermore relates to a device for controlling such hydraulic drive system which comprises a closed hydraulic circuit with a hydraulic pump and a hydraulic motor, comprising an actuating signal circuit for generating an actuating signal for the hydraulic pump and/or the hydraulic motor in dependence on a desired value of an output parameter of the hydraulic circuit. The invention finally relates to a crane and/or some other construction machine with a hydraulic drive system which comprises a closed hydraulic circuit with a hydraulic pump and a hydraulic motor, and to a control device for controlling the hydraulic drive system with an actuating signal circuit for generating an actuating signal for the hydraulic pump and/or the hydraulic motor in dependence on an output parameter of the hydraulic circuit.
Cranes, but also other construction machines, regularly have hydraulic drive systems with at least one closed hydraulic circuit, which has a hydraulic pump in combination with a hydraulic motor. By means of such hydraulic drive systems, various drive functions are realized for instance on cranes, and in particular hoisting winch drives, chain drives or wheel drives can be realized in this way. The hydraulic pump regularly is driven via a drive unit, such as an internal combustion engine. The hydraulic stream generated by the pump is translated into the corresponding actuating movement by the hydraulic motor coupled therewith. In order to control the corresponding actuating movement in a precise and stable way, the speed of the hydraulic motor must be controlled accordingly, the delivery rate of the hydraulic pump and the absorption volume of the hydraulic motor being adjustable, for instance by using adjustable types of swash plate for these components, but other types can be used as well. On the one hand, a fast response of the system should be achieved with corresponding operating or control commands. On the other hand, operating the actuators too fast or overriding the same can lead to instabilities of the drive system. Increasing the delivery rate of the hydraulic pump and/or the absorption volume of the hydraulic motor too fast can lead for instance to a strong deceleration of the drive unit or even a stalling of the diesel engine. Increasing the output torque too fast, for instance, can also lead to individual drive wheels spinning, when the system is used as a wheel drive and the vehicle moves for instance on a gravel road.